Widely used SSH library with remote code execution risk across many products.
CVE-2026-55200
libssh2 <=1.11.1: RCE via out-of-bounds packet_length in ssh2_transport_read.
Is CVE-2026-55200 being exploited?
Not confirmed. CVE-2026-55200 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 4.0% probability of exploitation in the next 30 days.
How severe is CVE-2026-55200?
CVE-2026-55200 is rated Critical with a CVSS score of 9.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55200?
Yes. A fix has been recorded for CVE-2026-55200. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55200 affect?
CVE-2026-55200 affects libssh2 <=1.11.1. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55200?
Upgrade to latest libssh2 (>=1.11.2) or apply patch.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attacker can cause heap corruption via oversized SSH packet_length, enabling RCE.
Immediate action required
- affected<= 1.11.1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.